The invention relates to a multi-feed circular knitting machine with needles, which can be controlled so as to assume a knitting and a non-knitting condition, and also selector jacks which are suspended in articulated manner in the needles, which jacks are pivotable as a body on to the cams by means of pivoting devices which act directly on the jacks, these jacks also being susceptible of being pivoted away from the cams, each needle having associated with it a butt which cooperates with a needle lowering cam in a cam track of each cam.
In the case of high speed circular knitting machines, with a relatively large number of feeds per machine, the highest permissible machine speed is substantially restricted by the fact that the non-knitting needles, which run through the particular feed mechanism of the machine on a so-called circular (guide) control path, run, with their butts which serve to lower the needles concerned, against the needle lowering control cam, when these needles are in their non-knitting position opposite the particular feed of the machine. As the cam track has a comparatively steep inclination in the vicinity of the needle lowering cam, these butts impact with considerable force on the needle lowering cam, as a result of which longitudinal vibration is set up in the needles. After the machine has been running for some time, this vibration can lead to needle breakage. Considerable wear of the needles and also of the cam parts is also caused.
In German published patent application No. 1,785,337 a multi-feed Jacquard circular knitting machine of the type described herein is also disclosed in whose needles, and needle jacks are suspended in articulated manner. In this known machine it is possible to prevent butts of non-knitting needles -- these butts being arranged on the needles and cooperating with the needle lowering cams -- from striking against the particular needle lowering cam concerned. To this end each needle jack has a butt for which a control surface of gentle inclination is arranged in each cam, this control surface serving to draw downwardly the needle jacks -- together with the non-knitting needles, associated with these jacks and also the needle lowering butts of these non-knitting needles -- before the needle lowering part is reached. This downwardly directed movement continues until the needle butts, which are being guided round the so-called circular guide (control) path, no longer strike against the needle lowering cam. In order to prevent this gently inclined control surface from acting on those needle jack butts which are associated with needles which are knitting, the cam part which defines the gently inclined control surface also defines a slide suface at the level of the track or path followed by the needle jack butts associated with the needles which are knitting, so that the needle jacks to which these butts are attached are pivoted away from the cam in front of the gently inclined control surface. Accordingly, this known Jacquard circular knitting machine requires the following elements: first pivoting devices, which are capable of pivoting needles (in principle it could be the needle jacks which are thus acted on) away from the cam at the selection station of each feed of the knitting machine, and which are also capable of pivoting these needles back onto the cam shortly after the selection station has been passed, thus ensuring that certain needles (as determined by the selection pattern) will not knit; cam parts, which define the above-mentioned gently defined control surface, and which guide the needle jack butts of non-knitting needles gently round the needle lowering cam of the feed concerned; also a second pivoting device in the form of a slide -- or contact -- surface, which serves to prevent the above-mentioned gently inclined control surface from acting on the needle jack butts of the needles which are knitting.
Underlying the present invention is the object of providing a circular knitting machine of the kind defined at the outset, in which it is possible with relatively simple structural means, to prevent the butts of non-knitting needles (these butts serving to lower the needles) from impacting against the needle lowering cams.